# Comparing POP to OOP **URL:** \ **Category:** Using Swift\ **Created:** [February 14, 2016, 11:59pm UTC](https://forums.swift.org/t/comparing-pop-to-oop/1438 "2016-02-14T23:59:05Z")\ **Posts on this page:** 1\ **Showing post:** 12
**Author:** ![dabrahams](https://sea2.discourse-cdn.com/swift/user_avatar/forums.swift.org/dabrahams/32/9815_2.png) [@dabrahams](https://forums.swift.org/u/dabrahams)\ **Post date:** [March 7, 2016, 4:53am UTC](https://forums.swift.org/t/comparing-pop-to-oop/1438/12 "2016-03-07T04:53:42Z")
> > > > > I have not read your blog. But in my opinion, what Apple called protocol > > > > > programming is actually so called functional programming. It is not object > > > > > programming at all. It uses protocols and structs to avoid object > > > > > programming. > > > > > > > > I don't think most functional programmers would recognize > > > > protocol-oriented programming as what they do. It is true that one of > > > > the main benefits we see in protocol-oriented programming is that it > > > > allows one to use \*mutable\* value types, instead of classes, in > > > > polymorphic contexts. Functional programming is largely concerned with > > > > immutable data, where the distinction between value and reference > > > > semantics disappears, and it doesn't matter if you're using classes or > > > > not. But the main thing in FP is the use of higher-order functions, > > > > which Swift enthusiastically supports, but have nothing whatever to do > > > > with protocol-oriented programming. > > > > > > Your e-mail touches on one of the things that excites me the most > > > about Swift. As you say “But the main thing in FP is the use of > > > higher-order functions, which Swift enthusiastically supports, but > > > have nothing whatever to do with protocol-oriented programming”. > > > Swift isn’t just a Protocol-Oriented programming language or an > > > Object-Oriented language or a functional programming language it is > > > actually all of them and more. While other languages attempt to > > > support different paradigms, in my opinion, Swift is one of the few > > > language that actually does a good job at supporting multiple > > > paradigms. > > > > > > In the conclusion section of my post, I mention that while I pointed > > > out a lot of ways that I believe POP is superior to OOP I would not > > > say that POP is a clear winner over OOP. > > > > It would be interesting to see where you think OOP has a distinct > > advantage due to fundamental properties of the paradigms (rather > > than artifacts of an immature implementation of protocol language > > features) > > I would not say that OOP has a distinct advantage over POP based on > the fundamental properties of the paradigms. However, if I were > pressed I would say that OOP does have an advantage over POP in the > area of data structures because of POP emphasis on value types over > reference types. “Protocol-oriented” doesn't mean “no reference types.” It means you're not forced into reference semantics just because you want polymorphism. > For example we cannot create a linked list with a value type. Not true, in fact.   enum List\ {      case Empty      indirect case NonEmpty(T, List)   }   var x: List = .NonEmpty(3, .NonEmpty(4, .Empty)) There are other ways, but that's the simplest in Swift. > If we tried we would get a compile time error that says: “Recursive > value type ‘Type’ is not allowed. > > There are two arguments that I could make off the top of my head > against my last statement. The first argument would be: Is preferring > value types to reference types actually part of OOP. I presume you meant POP. Being forced to use reference types is part of OOP. > I will address this in my next e-mail where you ask me what I mean by > my statement that POP is about so much more than the protocol. The > second argument would be that we are not limited to value types with > POP and we are able to still use reference types. Exactly. > While it is true that we are still able to use value types > with POP reference types? > however if we take Apple’s recommendation and use value types > for our custom types we really should try our best to avoid reference > types. It could get confusing if some of our types are reference > types and some are value types especially for larger enterprise type > projects. No, some things are fundamentally references, as I noted in the talk: [https://github.com/ASCIIwwdc/wwdc-session-transcripts/blob/master/2015/408.vtt#L3082](https://github.com/ASCIIwwdc/wwdc-session-transcripts/blob/master/2015/408.vtt#L3082) > Luckily in XCode with have the quick documentation where we can hold > down the option key and click on the type in question to tell us if it > is a value or reference type however we do not have that option > outside of the Apple’s ecosystem like when we are developing Linux > applications with Swift. Therefore we need to be careful on how and > when to use reference and value types. You always do need to be careful about that, regardless, because they have different semantics. > Where I really think OOP has a very distinct advantage of POP is that > it has been around for so long, has been vetted in more projects then > either of us can count and it is very well documented. Yes, that was the one argument I thought could be defensibly made for OOP over POP. > I don’t know if anyone can really say that Apple has documented what > POP is and isn’t very well Absolutely, we have not. > which is the reason I wrote my book on POP and why I plan on writing > additional posts on it as well. I'm looking forward to seeing more of that, and I like to help you capture more of what we mean by POP. > If you do a search on the Internet for Protocol-Oriented programming > you get a number of different views on what it is and what it isn’t. > Most of the articles, in my opinion, take a very narrow view of POP > and try to fit it into the OOP model but with an Interface first > approach which, once again in my opinion, misses the larger view. Yes! > **···** > > on Sun Mar 06 2016, Jon Hoffman \ wrote: > > > > On Mar 6, 2016, at 1:12 AM, Dave Abrahams via swift-users \ wrote: > > > on Sat Mar 05 2016, Jon Hoffman \ wrote: > > > > > > > > On Feb 25, 2016, at 7:35 PM, Dave Abrahams via swift-users \ wrote: > > > > > on Sun Feb 14 2016, zhaoxin肇鑫 \ wrote: > > > Once again I will explain this more in my next e-mail where I address > > your question about what I mean when I say that POP is about so much > > more than the protocol. > > > > Jon > > > > > > The winner is actually the programmer because we are not limited to > > > > one programming paradigm. We can choose the paradigm that fits our > > > > needs. Personally I have use POP in a number of projects and I > > > > definitely prefer it to OOP or FP but I would not criticize anyone > > > > that uses the other two because they are very valid paradigms that > > > > have proven over time. > > > > > > -- > > > -Dave > > > > > > \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ > > > swift-users mailing list > > > swift-users@swift.org > > > [https://lists.swift.org/mailman/listinfo/swift-users](https://lists.swift.org/mailman/listinfo/swift-users) > > -- > -Dave --- _[View the full topic](https://forums.swift.org/t/comparing-pop-to-oop/1438)._